After seeing how incredibly awesome my wife's MK9 was, I bought a K40 sight unseen... too heavy, sold it, bought an MK40... a little lighter, but too small for IWB carry (my opinion only) So I found it a GOOD home, and bought a P9, had problems, Kahr swapped me for a P40....
After all that, for an IWB gun, although I do love my P40, and can't even feel it back there, and it does feel half way comfortable now that I put an A-Grip on it... I wish I had stayed with my very first choice and learned to live with the weight.
IMHO, the Kahr K series is the most comfortable Sub-compact I've ever held..... Geez, it wasn't THAT heavy, it was just heavy for it's size.
So I second the K40 vote... I prefer that little extra bang over 1 more round... The recoil in a K40 is amazingly light. P40's got a lot more kick.
But if the .40 is out of the question for you, then K9 it is.